What ADuphily said. You only have to pay the $50 premium. After that, there's no charge, no matter how much you use it. (Although, if somebody developed a hack to use the 3G in a way it wasn't intended to be used and you used that hack, Amazon probably could and would block your Kindle's 3G.)

Keeping in mind that my knowledge is limited to how Amazon/Kindle works in the U.S.: The only time that you'd pay is if you use the 3G to download personal documents that you've emailed to your kindle, but that's easy to avoid by setting the personal document limit to $0.00 and using wifi to download the document.

Yep the 3G model is $50 more to cover the cost of the antenna. Then, you can browse and do whatever you want for free.

It's nothing to do with "the cost of the antenna". WiFi also requires an antenna . There is a minor cost associated with the cost of the 3G radio, but the price difference is essentially a market differentiator for a "premium product"; the difference in manufacturing costs is minimal.

Keeping in mind that my knowledge is limited to how Amazon/Kindle works in the U.S.: The only time that you'd pay is if you use the 3G to download personal documents that you've emailed to your kindle, but that's easy to avoid by setting the personal document limit to $0.00 and using wifi to download the document.

the price difference is essentially a market differentiator for a "premium product"; the difference in manufacturing costs is minimal.

While the latter is probably true, I doubt the former also holds - I would guess that there is not too much left for Amazon of the extra $50 after you take into account the data transfer costs that Amazon has to pay to AT&T and other providers around the world. Especially if you consider that people who do not plan to use 3G frequently would probably not get the 3G version. I would not even be surprised if Amazon was actually loosing money on the feature itself but then gained it back by (likely) better book purchases from the 3G devices.